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Publication numberUS20050223968 A1
Publication typeApplication
Application numberUS 11/089,814
Publication dateOct 13, 2005
Filing dateMar 25, 2005
Priority dateMar 26, 2004
Also published asUS7326293, US7799132, US20080092803
Publication number089814, 11089814, US 2005/0223968 A1, US 2005/223968 A1, US 20050223968 A1, US 20050223968A1, US 2005223968 A1, US 2005223968A1, US-A1-20050223968, US-A1-2005223968, US2005/0223968A1, US2005/223968A1, US20050223968 A1, US20050223968A1, US2005223968 A1, US2005223968A1
InventorsJohn Randall, Jingping Peng, Jun-Fu Liu, George Skidmore, Christof Baur, Richard Stallcup, Robert Folaron
Original AssigneeZyvex Corporation
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Patterned atomic layer epitaxy
US 20050223968 A1
Abstract
A patterned layer is formed by removing nanoscale passivating particle from a first plurality of nanoscale structural particles or by adding nanoscale passivating particles to the first plurality of nanoscale structural particles. Each of a second plurality of nanoscale structural particles is deposited on each of corresponding ones of the first plurality of nanoscale structural particles that is not passivated by one of the plurality of nanoscale passivating particles.
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Claims(27)
1. A method, comprising:
patterning a layer by removing each of a plurality of nanoscale passivating particles which each passivate a corresponding one of a first plurality of nanoscale structural particles forming the layer; and
depositing each of a second plurality of nanoscale structural particles on each of corresponding ones of the first plurality of nanoscale structural particles from which one of the plurality of nanoscale passivating particles was removed.
2. The method of claim 1 wherein each of the plurality of nanoscale passivating particles is one of a single passivating molecule and a single passivating atom, and wherein each of the first and second pluralities of nanoscale structural particles is one of a single structural molecule and a single structural atom.
3. The method of claim 1 wherein each of the plurality of nanoscale passivating particles is a single passivating atom, and wherein each of the first and second pluralities of nanoscale structural particles is a single structural atom.
4. The method of claim 1 further comprising repeating the patterning and the depositing to individually form each of a plurality of structural layers each having a thickness about equal to a thickness of one of the first plurality of nanoscale structural particles.
5. The method of claim 1 wherein depositing the second plurality of nanoscale structural particles forms a monolayer having a thickness about equal to one of the first plurality of nanoscale structural particles.
6. The method of claim 1 wherein the plurality of nanoscale passivating particles substantially comprises at least one of hydrogen atoms, chlorine atoms, HCl molecules, and methyl group molecules.
7. The method of claim 1 wherein the patterning includes at least one of:
individually removing each of ones of the plurality of nanoscale passivating particles with a scanning probe instrument, in a substantially serial manner; and
substantially simultaneously removing each of ones of the plurality of nanoscale passivating particles with a parallel array of scanning probes, in a substantially parallel manner.
8. The method of claim 1 wherein the patterning includes at least one of:
individually removing each of ones of the plurality of nanoscale passivating particles with one of a probe, a tip and a stamp, in a substantially serial manner; and
substantially simultaneously removing each of ones of the plurality of nanoscale passivating particles with one of a probe, a tip and a stamp, in a substantially parallel manner.
9. The method of claim 1 wherein the layer is located on a substrate comprising at least one of silicon and germanium, and the depositing is by atomic layer epitaxy of silicon employing hydrogen for passivation.
10. The method of claim 1 wherein the depositing is by liquid phase atomic layer epitaxy.
11. The method of claim 1 wherein at least one of the patterning and the depositing is at least partially automated.
12. The method of claim 1 wherein each of the first and second pluralities of nanoscale structural particles comprises a plurality of first nanoscale particles having a first composition and a plurality of second nanoscale particles having a second composition that is different relative to the first composition.
13. The method of claim 12 wherein the first plurality of nanoscale particles comprises a plurality of silicon atoms and the second plurality of nanoscale particles comprises a plurality of germanium atoms.
14. The method of claim 1 wherein the depositing includes growing the second plurality of nanoscale structural particles.
15. The method of claim 1 further comprising repeating the patterning and the depositing to individually form a plurality of structural layers, wherein the repeated patterning includes patterning a first pattern to which first ones of the plurality of deposited structural layers correspond and subsequently patterning a second pattern to which second ones of the plurality of deposited structural layers correspond.
16. A method, comprising:
patterning a layer by removing each of a first plurality of nanoscale passivating particles which each passivate a corresponding one of a first plurality of nanoscale structural particles forming the layer;
forming each of a second plurality of nanoscale structural particles on each of corresponding ones of the first plurality of nanoscale structural particles from which one of the first plurality of nanoscale passivating particles was removed, wherein each of the second plurality of nanoscale structural particles is passivated;
removing each of a second plurality of nanoscale passivating particles which each passivate a corresponding one of a third plurality of nanoscale structural particles forming the layer; and
forming each of a fourth plurality of nanoscale structural particles on each of corresponding ones of the third plurality of nanoscale structural particles from which one of the plurality of second plurality of nanoscale passivating particles was removed, wherein each of the fourth plurality of nanoscale structural particles is passivated.
17. The method of claim 16 wherein each of the first plurality of nanoscale passivating particles is substantially different in composition relative to each of the second plurality of nanoscale passivating particles, permitting their selective removal.
18. The method of claim 16 wherein a first process employed to remove the first plurality of nanoscale passivating particles is different relative to a second process employed to remove the second plurality of nanoscale passivating particles.
19. The method of claim 16 wherein each of the first and second pluralities of nanoscale structural particles have a first composition and each of the third and fourth pluralities of nanoscale structural particles have a second composition.
20. The method of claim 16 wherein a first one of the first and second compositions is silicon and a second one of the first and second compositions is germanium.
21. The method of claim 20 wherein the silicon is deposited from precursor gas dichlorosilane and the germanium is deposited from precursor gas dimethylgermane.
22. The method of claim 21 wherein passivating chemistry for silicon is one of chlorine and HCl and passivating chemistry for germanium is methyl groups, the depassivation of the methyl groups from the Ge employs atomic hydrogen, and the depassivation of HCl from Si is accomplished by raising the temperature of the sample to desorb the HCl from the Si while leaving the methyl groups passivating the Ge.
23. The method of claim 16 wherein the layer includes nanoscale particles of at least three different compositions, wherein the nanoscale particles includes at least one of molecules and atoms, and wherein a thickness of the layer is equal to a thickness of one of the at least one of molecules and atoms.
24. A method, comprising:
patterning a layer by placing each of a plurality of nanoscale passivating particles on a corresponding one of a first plurality of nanoscale structural particles forming the layer, wherein the layer comprises the first plurality of nanoscale structural particles and a second plurality of nanoscale structural particles and has a thickness about equal to a dimension of one of the first and second pluralities of nanoscale structural particles; and
depositing each of a third plurality of nanoscale particles molecules on each of corresponding ones of the second plurality of nanoscale structural particles.
25. The method of claim 24 wherein each of the first plurality of nanoscale structural particles has a first composition and each of the second plurality of nanoscale structural particles has a second composition that is substantially different relative to the first composition.
26. The method of claim 24 wherein placing includes substantially simultaneously placing ones of the plurality of nanoscale passivating particles in a procedurally parallel manner.
27. The method of claim 26 wherein placing includes substantially simultaneously placing ones of the plurality of nanoscale passivating particles with one of a probe, a tip and a stamp
Description

This application claims the benefit of U.S. Provisional Application No. 60/556,614, entitled “Patterned Atomic Layer Epitaxy,” filed Mar. 26, 2004, the entirety of which is hereby incorporated herein.

BACKGROUND

Atomic Layer Epitaxy (ALE) and Atomic Layer Deposition (ALD) have demonstrated the ability to provide layer-by-layer control in the deposition of atoms and/or molecules for many material systems using a variety of techniques. In each of these cases, the deposition process is cyclical, where a repeatable portion (less than, equal to, or somewhat greater than) of a monolayer is deposited with each full cycle. There are both gas phase and liquid phase ALE or ALD techniques for a wide range of materials. ALE or ALD processes have been developed for elemental semiconductors, compound semiconductors, metals, metal oxides, and insulators. There are ALE processes that involve the deposition of a self-limiting monolayer per cycle. For example, with gas phase gallium-arsenide (GaAs) ALE, a single monolayer of gallium (Ga) is deposited on a GaAs surface from trimethylgallium (TMG), where methyl groups passivate the gallium surface and limit the deposition to a monolayer. The TMG is pumped out and arsine is used to deposit a self-limiting layer of arsenide (As). The cycle is repeated to produce several layers of GaAs. It is also possible to substitute trimethylaluminium (TMA) instead of TMG. In this way, layered epitaxial structures, i.e., structures comprised of multiple layers, each layer in one monolayer, thus achieving atomic precision.

Various attempts have also been made for providing lateral patterning at the atomic level. One example involved using a scanning tunneling microscope (STM) to push xenon atoms across a nickel surface. Another example involved an approach for creating patterns in hydrogen atoms adsorbed on a silicon surface by getting them to desorb from the surface with electrical current from an STM that pumps energy into the silicon-hydrogen bond. The ability to selectively depassivate surfaces by removing an adsorbed monolayer of hydrogen is significant because there are ALE approaches which employ an adsorbed hydrogen layer as the self-limiting process.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 is a sectional view of at least a portion of one embodiment of a nanostructure in an intermediate stage of manufacture according to aspects of the present disclosure.

FIG. 2 is a sectional view of the nanostructure shown in FIG. 1 in a subsequent stage of manufacture according to aspects of the present disclosure.

FIG. 3 is a sectional view of the nanostructure shown in FIG. 1 in a subsequent stage of manufacture according to aspects of the present disclosure.

FIG. 4 is a sectional view of the nanostructure shown in FIG. 1 in a subsequent stage of manufacture according to aspects of the present disclosure.

FIG. 5 is a sectional view of the nanostructure shown in FIG. 1 in a subsequent stage of manufacture according to aspects of the present disclosure.

FIG. 6A is a sectional view of at least a portion of one embodiment of a nanostructure in an intermediate stage of manufacture according to aspects of the present disclosure.

FIG. 6B is a legend corresponding to FIG. 6A.

FIG. 6C is a sectional view of the nanostructure shown in FIG. 6A in a subsequent stage of manufacture according to aspects of the present disclosure.

FIG. 6D is a sectional view of the nanostructure shown in FIG. 6C in a subsequent stage of manufacture according to aspects of the present disclosure.

FIG. 6E is a sectional view of the nanostructure shown in FIG. 6D in a subsequent stage of manufacture according to aspects of the present disclosure.

FIG. 6F is a sectional view of the nanostructure shown in FIG. 6E in a subsequent stage of manufacture according to aspects of the present disclosure.

FIG. 7 is a sectional view of at least a portion of one embodiment of a nanostructure in an intermediate stage of manufacture according to aspects of the present disclosure.

FIG. 8 is a sectional view of the nanostructure shown in FIG. 7 in a subsequent stage of manufacture according to aspects of the present disclosure.

FIG. 9 is a sectional view of the nanostructure shown in FIG. 8 in a subsequent stage of manufacture according to aspects of the present disclosure.

FIG. 10 is a sectional view of the nanostructure shown in FIG. 9 in a subsequent stage of manufacture according to aspects of the present disclosure.

FIG. 11 is a sectional view of the nanostructure shown in FIG. 10 in a subsequent stage of manufacture according to aspects of the present disclosure.

FIG. 12 is a sectional view of the nanostructure shown in FIG. 11 in a subsequent stage of manufacture according to aspects of the present disclosure.

FIG. 13 is a sectional view of the nanostructure shown in FIG. 12 in a subsequent stage of manufacture according to aspects of the present disclosure.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

The present disclosure also includes references to “nanoscale particles” and various types of nanoscale particles. It is to be understood that, in the context of the present disclosure, a nanoscale particle is a single atom, a single molecule and/or another single particle having dimensions on the order of the dimensions of a single atom or a single molecule. Thus, a “nanoscale structural particle” may be a structural atom, a structural molecule, or another discrete, nanoscale particle of structure having atomic- or molecular-scale dimensions.

Referring to FIG. 1, illustrated is a sectional view of at least a portion of one embodiment of a nanostructure 100 in an intermediate stage of manufacture according to aspects of the present disclosure. Manufacturing according to aspects of this and other embodiments within the scope of the present disclosure includes performing patterned layer epitaxy, including patterned ALE and ALD, which may be carried out in a vacuum environment.

The nanostructure 100 includes a substrate 110 having a layer 120 formed thereon. The substrate 110 may be or include a bulk silicon (Si) substrate or a silicon-on-insulator (SOI) substrate, among others. The layer 120 may be or include a germanium (Ge) layer which may be deposited on, or grown from, the substrate 110. The layer 120 may also include more than one layer, including more than one Ge layer.

The nanostructure 100 also includes a passivation layer 130. In one embodiment, the passivation layer 130 substantially comprises a chlorine (Cl) layer. However, in other embodiments, the passivation layer 130 may have other compositions, and may include more than one layer. The nanostructure 100 may also include one or more layers other than those shown in FIG. 1.

Referring to FIG. 2, illustrated is a sectional view of the nanostructure 100 shown in FIG. 1 in a subsequent stage of manufacture, in which a pattern 135 has been formed. In the illustrated embodiment, the pattern 135 is formed by employing a scanning tunneling microscope (STM), wherein the tip 140 of the STM probe depassivates selected atoms, molecules and/or other nanoscale particles in the layer 120 by removing atoms, molecules and/or other nanoscale particles from the passivation layer 130. Consequently, a patterned passivation layer 135 may be formed. In other embodiments, a combination of photon and/or electron bombardment and STM induced field may be employed for depassivation.

Physical means could also be employed to create a patterned passivation layer. For example, a probe or tip operating on a single passivation atom, molecule and/or other nanoscale particle, or a stamp operating in parallel on several atoms, molecules and/or other nanoscale particles, may also be employed to remove the groups of atoms, molecules and/or other nanoscale particles from the passivation layer 130. For example, contacting the tip or stamp to the passivation atoms, molecules and/or other nanoscale particles being removed may create a bond that is stronger than that between the passivation atoms, molecules and/or other nanoscale particles and corresponding atoms, molecules and/or other nanoscale particles of the layer 120. Consequently, when the tip or stamp is removed, one or more passivation atoms, molecules and/or other nanoscale particles, or groups of passivation atoms, molecules and/or other nanoscale particles, may be removed from the layer 120 in a selective manner based on the configured pattern of the stamp. In a related embodiment within the scope of the present disclosure, a patterned passivation layer may be formed by transferring individual or groups of passivating atoms, molecules and/or other nanoscale particles from a probe, tip or stamp to the layer 120 (thus, adding material onto layer 120 as opposed to removing material from layer 120). For example, the passivating atoms, molecules and/or other nanoscale particles being added onto layer 120 may have a greater affinity for the surface of the layer 120 than the probe, tip or stamp. Thus, whether forming the patterned passivation layer by material addition or removal, the pattern of the patterned passivation layer may be atomically and/or molecularly precise, or otherwise precise at a nanoscale.

Referring to FIG. 3, illustrated is a sectional view of the nanostructure 100 shown in FIG. 2 in a subsequent stage of manufacture, in which a passivated monolayer 150 is formed on the exposed portions of the layer 120. In the illustrated embodiment, the passivated monolayer 150 comprises silicon 152 passivated by chlorine 154, although other embodiments may employ other compositions. The passivated monolayer 150 may be grown on the exposed portions of the layer 120, possibly at a temperature of about 575 C. with a dichlorosilane (DCS) process, and subsequently pumping out any residual gases. An exemplary DCS process is described below.

Referring to FIG. 4, illustrated is a sectional view of the nanostructure 100 shown in FIG. 3 in a subsequent stage of manufacture, in which all or a portion of the remaining passivated layer 120 is depassivated by removing all or a portion of the patterned passivation layer 135. Such depassivation may employ one or more processes substantially similar to the depassivation described above with respect to FIG. 2, possibly including the use of the STM probe tip 140, a combination of photon and/or electron bombardment and STM induced field, physical removal with a tip or stamp, or combinations thereof. In one embodiment, the layer 120 may be depassivated at a temperature of about 440 C. and may employ atomic hydrogen. Residual gases may then be pumped out. In some embodiments, depassivating the layer 120 using atomic hydrogen converts the chlorine 154 passivating the silicon 152 to HCl, yet the silicon remains passivated with the HCl.

Referring to FIG. 5, illustrated is a sectional view of the nanostructure 100 shown in FIG. 4 in a subsequent stage of manufacture, in which a passivated monolayer 160 is formed on the exposed portions of the layer 120. In the context of the present disclosure, a monolayer may be an atomic or molecular layer, having a thickness about equal to a dimension of the atoms or molecules forming the layer, or otherwise having a nanoscale thickness.

In the illustrated embodiment, the passivated monolayer 160 comprises germanium 162 passivated by a methyl group 164, although other embodiments may employ other compositions. The passivated monolayer 160 may be grown on the exposed portions of the layer 120, possibly at a temperature of about 500 C. with a dimethylgermane (DMG) process, and subsequently pumping out any residual gases.

Referring to FIG. 6A, illustrated is a schematic view of at least a portion of one embodiment of a nanostructure 200 in an intermediate stage of manufacture according to aspects of the present disclosure. FIG. 6B depicts a legend representing compositions of various parts of the nanostructure 200 according to one embodiment. However, embodiments within the scope of the present disclosure are not limited to the compositions depicted in the legend of FIG. 6B.

Aspects of the nanostructure 200 may be substantially similar to the nanostructure 100 shown in FIGS. 1-5 and/or otherwise described above. For example, the nanostructure 200 may be substantially similar to the nanostructure 100 shown in FIG. 5. The nanostructure 200 may undergo cyclic processing, as described below, to build silicon and germanium layers in the pattern established at the manufacturing stage shown in FIG. 6A, where the pattern may be established by aspects of the process shown in FIGS. 1-5 and described above.

The nanostructure 200 includes a first layer 210 which may substantially comprise germanium and may be substantially similar to the layer 120 described above. A second layer 220 includes an initial germanium pattern substantially surrounded by silicon. The germanium pattern is passivated with methyl groups and the silicon is passivated by HCl.

Referring to FIG. 6C, illustrated is a schematic view of the nanostructure 200 shown in FIG. 6A in a subsequent stage of manufacture in which the HCl passivating the silicon of the layer 220 is desorbed from the silicon by raising the temperature to about 575 C. Residual gases may subsequently be pumped out. Desorbing the HCl from the silicon may thus expose the silicon portion of the layer 220, yet the patterned germanium may remain passivated with the methyl groups.

Referring to FIG. 6D, illustrated is a schematic view of the nanostructure 200 shown in FIG. 6C in a subsequent stage of manufacture in which a monolayer 230 is formed over the depassivated silicon of layer 220. The monolayer 230 may comprise Cl-passivated silicon grown over the depassivated silicon with the DCS process described above, possibly at a temperature of about 575 C. Residual gases may subsequently be pumped out. At this stage, the germanium of layer 220 is protected from the growth process by the methyl group passivation.

Referring to FIG. 6E, illustrated is a schematic view of the nanostructure 200 shown in FIG. 6D in a subsequent stage of manufacture in which the germanium of layer 220 is depassivated by removing the methyl groups. The methyl groups may be removed by dropping the temperature of the process environment to about 450 C. and exposing the surface to atomic hydrogen. Residual gases may then be pumped out. Depassivation of the patterned germanium of layer 220 using atomic hydrogen may convert the Cl which passivates the silicon portion of layer 220 into HCl. Nonetheless, the silicon portion of layer 220 remains passivated by the HCl.

Referring to FIG. 6F, illustrated is a schematic view of the nanostructure 200 shown in FIG. 6E in a subsequent stage of manufacture in which a monolayer 240 is formed over the depassivated, patterned germanium of layer 220. The monolayer 240 may comprise methyl-group-passivated germanium grown over the unpassivated germanium portion of layer 220 using DMG at a temperature of about 450 C. The HCl passivation protects the silicon portion of layer 220 during this growth process. Residual gases may then be pumped out.

The cyclic process illustrated by FIGS. 6A-6F may be sequentially repeated to form the desired number of atomic, molecular, or otherwise nanoscale-precision layers (e.g., monolayers). In one embodiment, such sequential formation may be repeated for a first number of layers, each replicating a first pattern, and subsequently repeated for a second number of layers, each replicating a second pattern which may be somewhat or substantially different relative to the first pattern. Alternatively, or additionally, the earlier formed layers may have a first composition(s), and the subsequently formed layers may have a second composition(s) which may be substantially different relative to the first composition(s).

After completing the cyclic process illustrated by FIGS. 6A-6F a number of times, thereby forming a three-dimensional structure with atomic, molecular or otherwise nanoscale precision, the structure (e.g., the silicon structure of embodiments illustrated herein) can be released from the nanostructure 200, possibly by selectively etching the germanium with an NH4OH:H2O2 wet etch, which etches germanium aggressively but has an essentially zero etch rate for silicon. Consequently, a nanoscale-precision silicon structure can be formed and released from an underlying substrate.

The processes employed during the manufacturing stages shown in FIGS. 6A-6F, as well as other processes within the scope of the present disclosure, may be at least partially automated. That is, the processes and steps depicted in FIGS. 6A-6F and others can be amenable to automation and semi-automation, such as by well known registration and pattern recognition technology. Additional aspects of the at least partial automation of some embodiments within the scope of the present application are provided in commonly-assigned U.S. patent application Ser. No. 11/064,127, the entirety of which is hereby incorporated by reference herein. However, other aspects of automation and semi-automation are also within the scope of the present disclosure.

Referring to FIG. 7, illustrated is a schematic view of at least a portion of one embodiment of a nanostructure 300 in an intermediate stage of manufacture according to aspects of the present disclosure. Aspects of the nanostructure 300 may be substantially similar to the nanostructure 100 shown in FIGS. 1-5, the nanostructure 200 shown in FIGS. 6A-6F, and/or otherwise described herein. The nanostructure 300 may undergo cyclic processing, as described below, to build silicon and germanium layers in the pattern established at the manufacturing stage shown in FIG. 7. At the manufacturing stage shown in FIG. 7, the nanostructure 300 includes a substrate 310 and a layer 320.

The substrate 310 may be substantially similar to the substrate 110 shown and described in reference to FIG. 1. In one embodiment, the substrate 310 presents an atomically flat silicon surface, possibly having a <100> crystallographic orientation.

In the example embodiment illustrated in FIG. 7, a portion 322 of the layer 320 substantially comprises germanium atoms and another portion 324 substantially comprises silicon atoms. The atoms of each of the germanium portion 322 and the silicon portion 324 are passivated by chlorine atoms 326. Of course, as with embodiments described above, the scope of the present disclosure is not limited to embodiments substantially comprising germanium and silicon as structural elements, or to embodiments substantially employing chlorine (or HCl) as passivation elements, or to embodiments in which the layer 320 and other layers are limited to atomic-scale monolayers, such that other embodiments within the scope of the present disclosure may employ alternative or additional materials, molecular-scale monolayers, and/or nanoscale monolayers.

Referring to FIG. 8, illustrated is a schematic view of the nanostructure 300 shown in FIG. 7 in a subsequent stage of manufacture in which an STM probe tip 140 is employed to depassivate the silicon. Consequently, the passivating chlorine atoms 326 of layer 320 are removed from the silicon portion of the layer 320.

Referring to FIG. 9, illustrated is a schematic view of the nanostructure 300 shown in FIG. 8 in a subsequent stage of manufacture in which a monolayer 330 of silicon 332 with chlorine passivation 334 is formed over the unpassivated silicon portion of layer 320. The monolayer 330 may be grown with DCS at 575 C.

Referring to FIG. 10, illustrated is a schematic view of the nanostructure 300 shown in FIG. 9 in a subsequent stage of manufacture in which the germanium portion of layer 320 is depassivated. Consequently, the passivating chlorine atoms 326 over layer 320 are removed from the germanium portion 322 of layer 320. The depassivation may be achieved by dropping the temperature to 500 C. or lower and exposing the surface to atomic hydrogen. In some embodiments, the depassivation of the germanium portion 322 of layer 320 converts the chlorine atoms passivating the silicon 332 of layer 330 to HCl. Nonetheless, the silicon 332 of layer 330 remains passivated.

Referring to FIG. 11, illustrated is a schematic view of the nanostructure 300 shown in FIG. 10 in a subsequent stage of manufacture in which a monolayer 340 of germanium 342 with methyl group passivation 344 is formed over the unpassivated germanium portion of layer 320. The monolayer 340 may be grown at 500 C. using DMG.

Referring to FIG. 12, illustrated is a schematic view of the nanostructure 300 shown in FIG. 11 in a subsequent stage of manufacture in which the methyl-passivated-germanium 340 is depassivated by removing the methyl groups 344 and the chlorine-passivated-silicon 330 is depassivated by removing the chlorine 334. The respective depassivations can occur simultaneously or sequentially, such as by raising the temperature above 500 C., possibly employing atomic hydrogen.

Referring to FIG. 13, illustrated is a schematic view of the nanostructure 300 shown in FIG. 12 in a subsequent stage of manufacture in which the depassivated germanium 342 and silicon 332 are passivated by dosing with molecular chlorine 350. The cyclic process of FIGS. 7-13 can be sequentially repeated to grow additional germanium and silicon layers with atomic precision. Moreover, the cyclic process, and repetitions thereof, can be implemented as one or more automated or semi-automated processes.

After the desired number of atomic layers are grown, the silicon structures (324, 332, etc.) can be released by selectively etching the germanium. For example, an NH4OH:H2O2 wet etch may be employed to selectively etch the germanium, although alternative or additional etching compositions and/or selective etch processes are also within the scope of the present disclosure.

In the above description of exemplary embodiments according to aspects of the present disclosure, a dichlorosilane (DCS) process may be used during certain stages. Generally, dichlorosilane (SiCl2H2 DCS) and hydrogen (H2) may be used as precursor gases, and the process may be performed at a constant temperature of about 575 C. In one embodiment, the process is performed in a load-locked, turbomolecular, pumped system, with a base pressure of about 310−9 Torr, or possibly a lower pressure. The load lock chamber may have a base pressure of 510−7 Torr. Mass flow controllers (MFC) and a conductance valve may be used to control the pressure and residence time of the gases in the chamber. A tungsten filament may be heated to about 2000 C., at least during part of the deposition cycle, to crack H2 into atomic hydrogen. A sample heater may be used to keep the sample at the operating temperature of about 575 C.

One reaction that leads DCS to sub-monolayer per cycle deposition is:
SiCl2H2(g)+4_→SiCl(a)+Cl(a)+2H(a)
where (g) refers to the gas phase, (a) indicates surface adsorbed atoms or molecules and 4_indicates four active surface states on the Si surface.

DCS may break down in the gas phase according to the following, although in some embodiments SiClH is not the dominant gas species:
SiCl2H2(g)→SiClH(g)+HCl(g).

A potential description of a reaction at 575 C. where the H will desorb and result in a Cl passivated monolayer of Si is:
SiClH(g)+2_→SiCl(a)+H(a)→SiCl(a)+H(g)

The passivation layer of Cl may be removed by thermally cracking H2 to make atomic H, which reacts with the Cl to make HCl, which thermally desorbs from the Si surface.
SiCl(a)+H(g)→Si(a)+HCl(g)

With the Si sample at a constant 575 C., the Si ALE cycle may proceed as follows:

    • 1) DCS introduced to the chamber at a pressure of about 17 mTorr for a duration of about 20 seconds;
    • 2) DCS pumped from the chamber for about 20 seconds;
    • 3) H2 introduced to the chamber at a pressure of about 0.5 mTorr, where the tungsten filament is held at about 2000 C. for about 15 seconds; and
    • 4) H2 evacuated from chamber for about 30 seconds.

According to aspects of another embodiment of the processes described above, silicon and germanium atomic layer epitaxy (ALE) processes can be integrated to achieve atomic, molecular, or otherwise nanoscale precision patterning which may be employed as an improved process for producing monochlorosilane (MCS, SiClH). Current methods for producing monochlorosilane require adjusting pressure, residence time, and sample temperature to produce MCS “in the vicinity of the heated sample” with a poorly understood gas phase process.

However, according to aspects of the present disclosure, the improved process for producing MCS provides for more deliberate processes in the gas phase, such as thermal or microwave dissociation, which could be used to significantly improve the ratio of MCS to DCS in the gas phase, result in fewer defects, and possibly a wider window for deposition a single monolayer per cycle.

According to another example of an improved process for producing MCS, the MCS is separated via ionization, mass separation and neutralization. Consequently, MCS may be the exclusive, or at least the dominant, species arriving at the surface.

According to some embodiments within the scope of the present disclosure, silicon chloride or germanium chloride radicals may be delivered directly to the surface, which may improve monolayer deposition over a large temperature range, possibly with few or no vacancies created by the need to deposit extra hydrogen on the surface. In one such example, SiH and GeH radicals could provide ALE processes that require hydrogen depassivation only.

In the processes described above and otherwise within the scope of the present disclosure, one example of a tool for implementing atomically precise manufacturing (APM) methods includes an STM or other scanning probe instrument. Moveable tethers may also be employed to handle releasable parts. Other tools which may alternatively or additionally be employed include a nanomanipulator, including those having multiple tips, and/or a MEMS-based nanopositioning system. Such tools can further comprise software and systems to operate the APM methods described herein as an automated or semi-automated process.

An extensively parallel patterned ALE tool may also be employed as part of a nanomanufacturing system. One example of such a parallel patterned ALE tool may include a microautomation effort for developing an assembly system architecture.

One or more embodiments of the methods and/or tools described herein may provide or enable one of more of the following, where A and B components represent different atomic, molecular and/or nanoscale feedstock or building materials, such as germanium and silicon atoms:

    • Full monolayer deposition per cycle;
    • A passivating chemistry that can be locally depassivated with a scanning probe;
    • Atomic, molecular and/or nanoscale precision depassivation;
    • Reasonable conductivity in the substrate on which the passivation layer is formed;
    • A substrate comprising a robust mechanical material;
    • A substrate comprising a flexible material system where A and B components can be grown;
    • Etch selectivity between such A and B components;
    • Atomic, molecular and/or nanoscale precision in all 3 dimensions;
    • Multiple patterning for complex structures;
    • Heteroepitaxy in multiple dimensions (A and B materials);
    • The use of A and B materials for scaffolding and as a sacrificial layer; and
    • Templated, selective ALE growth of AB monolayers.

In addition, the ability to fill each monolayer with A and B nanoscale particles as described herein can provide or enable, in some embodiments, one or more of the following:

    • Patterning can be done on a substantially flat surface, or at worst, one with single layer nanoscale particle step edges, which is particularly suitable for STM patterning;
    • Developing an etch for B nanoscale particles that has a high selectivity over A nanoscale particles, which may enable use of B nanoscale particle volumes as a sacrificial layer, possibly permitting A nanoscale particle structures to be releasable;
    • Providing A and B components where there is some etch selectivity between A and B components may enable the creation of complex three-dimensional structures that are releasable from the substrate by depositing complete monolayers of part A nanoscale particles and part B nanoscale particles where the patterning defined which areas were A nanoscale particles and which were B nanoscale particles;
    • With the B nanoscale particles being used as scaffolding, relatively complex structures of A nanoscale particles may be constructed; and
    • The stability of the structure during growth may be better than if A nanoscale particles were not constrained laterally, and concerns about growth on exposed sidewalls may be eliminated.

Although the examples of methods and tools described herein may sometimes refer to specific constituents, alternatives are available within the scope of the present disclosure. For example, in addition to deposition processes described above, the materials selected for A and B may additionally or alternatively be deposited via diamond chemical-vapor-deposition (CVD), thus providing a diamond-based ALE approach.

Other considerations regarding the myriad embodiments within the scope of the present disclosure regard the materials selected for A and B. That is, the materials selected for A and B may both comprise metals, in contrast to germanium and silicon in the exemplary embodiments described above. Where A and B both comprise metals, the methods disclosed herein may be adjusted to compensate for potential stability issues that may be encountered as metal nanoscale particles reside on a metal substrate. Also, the materials for A and B (metallic or otherwise) may be selected to have similar or substantially equal lattice constants. In other embodiments, the materials for A and B may be selected to have lattice constants which differ by less than about 5%, 10%, 20% or some other predetermined variance, possibly depending on the degree of adhesion between the materials A and B and/or the underlying substrate.

The materials selected for A and B may also or alternatively comprise metal oxides, such as Al2O3. When A and B comprise metal oxides, depassivation techniques employed in methods discloses herein may be adjusted, such as where the passivation chemistry may be either methyl or hydroxyl groups, where trimethylaluminum (TMA) may be used to react with the OH groups and deposit methyl passivated Al, and H2O may be used to replace the methyl groups and deposit OH groups.

Embodiments according to aspects of the present disclosure may also substitute carbon, a carbon alloy and/or a carbon compound for the silicon and/or germanium in one or more layers and/or the underlying substrate of the embodiments described above. In embodiments employing selective etch processing, however, selecting material substitutions for silicon and/or germanium should take into account the selectivity (i.e., etch resistivity) of the substitute materials. Such a consideration may be less critical where alternatives to selective etching may be employed.

Other materials may also be substituted for the above-described use of hydrogen. For example, many embodiments may replace or augment the hydrogen with a methyl group, an ethyl group, and/or other univalent or monovalent radicals, among other compositions. Similarly, many embodiments may replace or augment the above-described use of chlorine with another halogen, among other compositions.

Methods of atomically, molecularly and otherwise nanoscale precise manufacturing described herein may also be implemented in a liquid phase process. According to one example of a liquid phase process, the materials selected for A and B may comprise insulating materials, such as sapphire.

In addition, although a scanning tunneling microscope is used as the scanning probe microscope in several of the methods and tools described herein, other suitable scanning probe microscopes include but are not limited to atomic force microscopes (AFMs). In an example where an AFM is used, the patterning technique may be described as AFM based nanolithography.

The methods and tools described herein can be used to grow releasable silicon nanostructures with atomic, molecular or otherwise nanoscale precision. One example of a nanostructure that could be so made is a nanopore, which is a 2 nm aperture in a thin (˜2 nm) membrane. A single nanopore can be an enormously valuable component of a tool that sequences DNA. The pore could separate two volumes of electrolyte solution and an ionic current through the nanopore may be measured. A strand of DNA can the be pumped through the nanopore. As the DNA goes through the pore, the ionic current can be modified in a way that depends on the base that is in the pore. In this way, very long strands of DNA may be read at a rate exceeding one base per millisecond. A single nanopore may sequence the entire human genome in a month. With 500 nanopores, the entire gene sequence of an individual may be read in 2 hours. With atomically precise nanopores made according to the methods described herein, even a single serial prototype tool could produce very significant value. Other exemplary nanostructures that could be prepared according to the present methods include atomically precise tips, nano machine parts, and structural parts (bricks, plates, beams, etc.).

Thus, among other aspects, the present disclosure introduces a method comprising, at least in one embodiment, patterning a layer by removing each of a plurality of passivating molecules which each passivate a corresponding one of a first plurality of structural molecules forming the layer. Each of a second plurality of structural molecules is then deposited on each of corresponding ones of the first plurality of structural molecules from which one of the plurality of passivating molecules was removed.

Another embodiment of a method according to aspects of the present disclosure includes patterning a layer by removing each of a first plurality of passivating molecules which each passivate a corresponding one of a first plurality of structural molecules forming the layer. Each of a second plurality of structural molecules is then formed on each of corresponding ones of the first plurality of structural molecules from which one of the first plurality of passivating molecules was removed, wherein each of the second plurality of structural molecules is passivated. Each of a second plurality of passivating molecules is then removed, the second plurality of passivating molecules each passivating a corresponding one of a third plurality of structural molecules forming the layer. Each of a fourth plurality of structural molecules is then formed on each of corresponding ones of the third plurality of structural molecules from which one of the plurality of second plurality of passivating molecules was removed, wherein each of the fourth plurality of structural molecules is passivated.

Another embodiment of a method according to aspects of the present disclosure includes patterning a layer by placing each of a plurality of passivating molecules on a corresponding one of a first plurality of structural molecules forming the layer, wherein the layer comprises the first plurality of structural molecules and a second plurality of structural molecules. Each of a third plurality of structural molecules is then deposited on each of corresponding ones of the second plurality of structural molecules. Aspects of two or more of these embodiments may also be combined as additional embodiments within the scope of the present disclosure.

The foregoing has outlined features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure.

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US8318248 *Jun 4, 2009Nov 27, 2012Uchicago Argonne, LlcSpatially controlled atomic layer deposition in porous materials
US8496999 *Mar 24, 2009Jul 30, 2013The Board Of Trustees Of The Leland Stanford Junior UniversityField-aided preferential deposition of precursors
US20090258157 *Mar 24, 2009Oct 15, 2009Neil DasguptaField-aided preferential deposition of precursors
US20090304920 *Jun 4, 2009Dec 10, 2009Uchicago Argonne, LlcSpatially controlled atomic layer deposition in porous materials
Classifications
U.S. Classification117/94, 117/104, 117/936, 117/92, 117/97, 117/91
International ClassificationC30B29/08, C30B28/12, C30B28/14, C30B23/00, C30B25/14, C30B25/04, C30B25/00
Cooperative ClassificationC30B25/14, C30B25/04
European ClassificationC30B25/04, C30B25/14
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